A sod harvester usually has a horizontal blade which severs the sod from the ground at the desired thickness in combination with two vertical side blades which cut the sod to the desired width. Thus, a continuous strip of sod is formed as the harvester travels along its cutting path. A transverse vertical cutter blade is periodically driven into the sod adjacent the undercutting blade to cut the strip to length.
As the strip of sod is cut, it is conveyed away from the cutter blade, usually up an inclined conveyor, for forming into rolls. U.S. Pat. No. 3,509,944 (Brouwer et al.) discloses a prior art sod harvester which includes such an inclined conveyor, and in which the rolls of sod are formed adjacent the upper end of the conveyor. The sod harvester disclosed in the '944 patent is designed to be mounted at the side of a power unit, by which the harvester is propelled.
U.S. Pat. No. 4,832,130 (Brouwer et al.) discloses a self-propelled sod harvester. The harvester includes an inclined conveyor which delivers the strip of sod into a separate roll-forming enclosure which includes a pair of conveyors disposed generally at right angles to one another for forming the roll. The formed rolls are discharged onto a cart at the end of the harvester which can convey the formed roll to either side of the cart and clear of the harvester on its next pass. The '130 patent also discloses a curved conveyor for discharging formed rolls clear of the harvester.
Robots have long been used in industry to replace human operators doing repetitive manual operations. They have the advantages of consistency, accuracy, speed, and tirelessness. Automated processes or automatic machines share these advantages, but robots have the additional advantage of flexibility. In other words, automatic machines are capable of doing a single repetitive operation, while robots can be programmed to do a variety of operations. Robots derive this advantage from two things. First, the method of control is programmable, usually with a computer. Second, the mechanical manipulator is capable of a wide variety of motions.
Most commonly, robots have a fixed base. They do their work always at the same location. Examples include welding, painting, moving workpieces or tooling, and palletizing material. There also exist mobile robots, capable of moving from place to place. Examples of mobile robots include vehicles for moving material within a factory, or picking and moving goods within a warehouse. Generally, the flexible, programmable function of these robots include the carrying or moving of an object from one place to another.
There also exist automatic machines that gather and stack agricultural products. Examples include automatic bale wagons for gathering and stacking rectangular bales of hay, and automatic machines for loading and stacking cartons in an agricultural field. However, these prior machines lack the programmability and flexible manipulators of a robot.
At least for the last twenty years there has been an awareness of a need for automatic stacking of sod at the point of collection, or harvesting. Throughout that time, industrial robots were well-known to be in existence. Also, throughout that time there has been an awareness that sod growers in different regions use different sizes of sod rolls and different configurations of stacks of sod rolls. Even so, during that time the only machines developed for that purpose have been automatic stackers, relatively large, not programmable, and dedicated to a single size or method of stacking. In addition, it has been common practice to stack sod manually in a way that the top layers of the stack are smaller than lower layers, in order to enhance the stability of the stack. No mechanical stacker has provided a way to accomplish this method of stacking.